Time code transmission method and time code transmission apparatus

ABSTRACT

As a pre-processing step for transmitting a timecode, a checking information is retrieved from a linear time code (LTC). A checking data is created using the retrieved checking information. The checking data is superimposed on a vertical interval time code (VITC). As a post-processing step for transmitting a timecode, meanwhile, collating information corresponding to the checking information is retrieved from the LTC. A collating data is created using the retrieved collating information. Then, the checking data is retrieved from the received VITC. The retrieved checking and collating data are collated to verify, thereby, the presence or absence of errors in the received LTC.

TECHNICAL FIELD

The present invention relates to a method of and an apparatus fortransmitting a timecode which is created to be superimposed on an imagesignal.

BACKGROUND TECHNIQUE

A timecode superimposed on an image signal includes LTC (LinearTimecode), which is, as a consequence of the biphasemark modulation,recorded in the band of audio frequencies, and VITC (Vertical IntervalTimecode), which is, as a consequence of the NRZ modulation, transmittedat vertical intervals.

These timecodes are subject to the occurrence of errors (change of thedata content), which is caused by defective retrieval or transmissionwhen reproduced by a reproducing apparatus or transmitted. Such errorscause the accuracy of the timecodes to degrade, therefore it isnecessary to detect with high accuracy any error occurred in thetimecodes. To be able to detect the errors will offer options such aschoosing not to use any erroneous timecode or amending any erroneousportion in the timecode by applying a predetermined processing thereto.

In this regard, the VITC includes in the data thereof CRC code (CyclicRedundancy Checking Code), by which the occurrence of errors can bedetected with high accuracy. However, no methods or structures fordetecting errors in the LTC have ever been implemented, and neither hasany effective suggestion been advanced.

Therefore, a main object of the present invention is to provide a methodof and an apparatus for transmitting a timecode capable of effectivelydetecting errors occurred in the LTC.

DISCLOSURE OF THE INVENTION

1. In order to achieve the object, the present invention has thefollowing structure:

A timecode transmission method for simultaneously transmitting LTC(Linear timecode) and VITC (Vertical Interval Timecode) which arecorrelated according to the present invention includes, as apre-processing step when transmitting a timecode, a step of retrieving achecking information from the LTC to create a checking data using theretrieved checking information and a step of superimposing the checkingdata on the VITC.

The present invention further includes, as a post-processing step afterthe timecode has been received, a step of retrieving a collatinginformation corresponding to the checking information from the receivedLTC to create a collating data using the retrieved collating informationand a step of retrieving the checking data from the received VITC andcollating the retrieved checking data with the collating data to verifythe presence or absence of errors in the received LTC.

A timecode transmission method and apparatus according to the presentinvention characterized in the foregoing description is capable ofverifying with high accuracy errors occurred in the LTC at the time ofreproduction and transmission by collating the checking data retrievedfrom the received VITC with the collating data created from the receivedLTC.

In this case, it is preferable; in the pre-processing step whentransmitting the timecode, to retrieve the checking information from theLTC at preset retrieving positions therein, while superimposing thechecking data on the VITC at entry positions therein corresponding tothe retrieving positions in the LTC; in the post-processing step afterthe timecode has been received, to retrieve the collating informationfrom the received LTC at the retrieving positions therein. By doing so,the presence or absence of errors occurred in the LTC can be detectedcorresponding to the preset retrieving positions in the LTC.

According to the present invention, it is preferable to set theretrieving positions in every frame unit of an image signal so that thepresence or absence of errors occurred in the retrieving positions inthe LTC can be thereby verified per frame.

According to the present invention, it is preferable to, first, retrievea plurality of checking and collating information from every retrievingposition, and then execute a calculation processing to the retrievedplural information based on a predetermined calculation formula whencreating the checking and the collating data. In this manner, errorsoccurred in the plural information constituting the LTC can becollectively detected at a time.

According to the present invention, it is preferable to retrieve thechecking and the collating information from a user's bit in the LTC sothat errors in the LTC user's bit can be thereby verified.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a block view showing a structure of an apparatus fortransmitting a timecode according to a mode for executing the presentinvention.

THE BEST MODE FOR CARRYING OUT THE INVENTION

Below described in detail is the best mode for executing the presentinvention with reference to FIG. 1. FIG. 1 is a block view showing astructure of an apparatus for transmitting a timecode according to thebest mode for executing the present invention.

A timecode transmission apparatus 1 comprises a transmitter 2 and areceiver 3. The transmitter 2 comprises a LTC generating unit 4, a VITCgenerating unit 5, an image auxiliary information generating unit 6, afirst superimposing unit 7, a second superimposing unit 8, a firstchecking information retrieving unit 9, a checking data creating unit 10and a transmitter 11.

The receiver 3 comprises a receiving unit 12, a second checkinginformation retrieving unit 13, a collating data creating unit 14, achecking data retrieving unit 15, and a verifying unit 16 and a VITCerror detecting unit 17. The LTC generating unit 4 generates LTC. TheVITC generating unit 5 generates VITC. The LTC and VITC are generated ina correlated status corresponding to an image signal not shown. Theimage auxiliary information generating unit 6 generates an imageauxiliary information corresponding to respective frames in an imagedata. The image auxiliary information will be described later.

The first superimposing unit 7 superimposes the image auxiliaryinformation on the LTC. The first checking information retrieving unit 9retrieves a checking information from the LTC at respective framepositions therein. The retrieved checking information will be describedin detail later.

The checking data creating unit 10 creates a checking data from thechecking information retrieved by the first checking informationretrieving unit 9. The method of creating the checking data will bedescribed later.

The second superimposing unit 8 superimposes the image auxiliaryinformation and the checking data on the VITC. The transmitting unit 11transmits the LTC and VITC to the receiver 3. It is unnecessary torestrict the method of the transmission, for which a wire or wirelesstransmission may be an option.

The receiving unit 12 receives the LTC and VITC transmitted from thetransmitter 2. The second checking information retrieving unit 13retrieves a collating information from respective frame positions in thereceived LTC.

The collating information is retrieved by the second checkinginformation retrieving unit 13 in the same manner as the checkinginformation is retrieved by the first checking information retrievingunit 9. The details will be described later.

The collating data creating unit 14 creates a collating data through acalculation processing using the collating information retrieved by thesecond checking information retrieving unit 13 based on a predeterminedcalculation formula.

The checking data retrieving unit 15 retrieves the checking data fromthe received VITC. The verifying unit 16 collates the checking data withthe collating data to verify the presence or absence of errors occurredin the received LTC. The VITC error detecting unit 17 executes thecyclic redundancy check using a CRC cord superimposed on the VITC todetect the presence or absence of errors occurred in the received VITC.

Referring to the figure, a reference numeral 18 shows a LTC outputterminal for outputting LTC received by a receiving unit 12 from areceiver 3 to outside. 19 shows a verification result output terminalfor outputting a verification result by a verifying unit 16 from thereceiver 3 to outside. 20 shows a VITC output terminal for outputtingVITC received by the receiving unit 12 from the receiver 3 to outside.21 shows a VITC error detection result output terminal for outputting anerror detection result by a VITC error detecting unit 17 from thereceiver 3 to outside. 22 shows a recording/reproducing apparatus forrecording generated LTC and VITC on a transmitter 2 side and reproducingthe recorded LTC and VITC upon a request from the transmitter 2 side tooutput them to a transmitter 2.

According to the mode for executing the present invention, the firstchecking information retrieving unit 9 and the checking data creatingunit 10 constitute a checking data creating apparatus. The secondsuperimposing unit 8 constitutes a superimposing apparatus. The secondchecking information retrieving unit 13 and the collating data creatingunit 14 constitute a collating data creating apparatus. The checkingdata retrieving unit 15 and the verifying unit 16 constitute a verifyingapparatus. However, the described structures are an example of executingthe present invention. Needless to say, the present invention acceptsany structure capable of exerting the functions cited in the claims.

The image auxiliary information is hereby described. As an example ofthe image auxiliary information, an effective frame information can bementioned. The effective frame information is hereby explained. An imagedata corresponding to an optional image format may occasionally beconverted to an image data corresponding to an image format having anumber of frames per second different than that of the optional imageformat. Such a conversion results in an increased or decreased number offrames per second.

When executing the format conversion which results in an increasednumber of frames per second, the amount of an image data constitutingthe frames (hereinafter referred to as frame image data) increases afterthe conversion. Therefore, at least one frame image data out of theframe image data prior to the conversion is, as a frame image data,redundantly written in the image data after the conversion

In the case of the format-converted image data as described, it isrequired to selectively pick an effective frame image data out of theredundantly recorded frame data (of the redundantly written data, onewhich is the closest time-wise to a real time position at the time ofrecording). The reason for that is to reduce a recording capacity at thetime of nonlinear editing, and so on.

When such a format conversion is executed, the following processing isapplied to the timecode. In the timecode corresponding to the imageformat after the conversion, a flag information is superimposed to berecorded at a frame position corresponding to an effective frame. In thetimecode corresponding to the image data after the format conversion,the effective frame is designated according to the effective frameinformation. The flag information equals the effective frameinformation.

Hereinafter is described a method of transmitting a timecode using thetimecode transmission apparatus according to the mode for executing thepresent invention.

To start, a step executed by the transmitter 2 is described. Firstly,the LTC generating unit 4 generates LTC. The VITC generating unit 5generates VITC. The image auxiliary information generating unit 6generates an image auxiliary information.

Then, the image auxiliary information is superimposed on the LTC by thefirst superimposing unit 7. The image auxiliary information issuperimposed by being written in respective user's bits (binary group)set in respective frame information in the LTC. The LTC having the imageauxiliary information superimposed thereon is outputted to thetransmitting unit 11.

The LTC outputted to the transmitting unit 11 is also supplied to thefirst checking information retrieving unit 9. The first checkinginformation retrieving unit 9 retrieves a checking information from thesupplied LTC. The checking information comprises, for example, a bitinformation constituting the information unit of a data groupconstituting the respective frame information in the LTC (eg. four bitinformation constituting the information unit of the data group). Thefirst checking information retrieving unit 9 retrieves the checkinginformation from the LTC at every frame therein. The first checkinginformation retrieving unit 9 retrieves a plurality of checkinginformation at every frame unit of an image signal. The first checkinginformation retrieving unit 9 can determine the checking information tobe retrieved by identifying the retrieving positions in the checkinginformation to be retrieved. Below is the description based on theassumption that four kinds of checking information A–D are retrievedfrom the LTC at every frame unit therein.

The checking information A–D retrieved by the first checking informationretrieving unit 9 is supplied to the checking data creating unit 10. Achecking formula is precedently set and recorded in the checking datacreating unit 10. The checking formula can adopt a variety ofcalculation formulas such as an addition, multiplication, division orother formulas, or a compound formula with some of them combined can beused. Below is the description based on the case of adopting anaddition.

The checking data creating unit 10 executes a calculation processing tothe supplied checking information A–D according to a stored formula.This case is based on the assumption that a calculation result (A+B+C+D)is obtained according to the calculation processing using an addition.

The checking data creating unit 10 outputs the calculation result(A+B+C+D) as a checking data. The checking data is outputted per framein the LTC. For reference, when the calculation is executed and thecalculation result (A+B+C+D) produces a large quantity of data, theinformation of a few lower bits in the calculation result (A+B+C+D) (eg.eight bits) may be employed as the calculation result.

The checking data is supplied to the second superimposing unit 8. Theimage auxiliary information is, together with the checking data,supplied to the second superimposing unit 8, which superimposes thechecking data and the image auxiliary information on the VITC. Thechecking data is, together with the image auxiliary information,superimposed, for example, by being written in the respective user'sbits (binary group) constituting respective frame information in theVITC. The VITC with the checking data and the image auxiliaryinformation superimposed thereon is outputted to the transmitting unit11, and the LTC and the VITC are, as the need arises, outputted to therecording/reproducing apparatus 20 to be recorded therein. Further, therecording/reproducing apparatus 20, as the need arises, reproduces therecorded LTC and VITC to output them to the transmitter 2 (morespecifically, the transmitting unit 11).

The transmitting unit 11 transmits the LTC and VITC generated in thetransmitter 2 and the LTC and VITC supplied by the recording/reproducingapparatus 20 to the transmitter 3. The transmitting unit 11 transmitsthe LTC and VITC in the coordinated status. In that case, errorspossibly occur in the data constituting the transmitted LTC and VITC dueto instabilities in transmission or reproduction on therecording/reproducing apparatus 20 and so on.

A step executed by the receiver 3 is described below.

The LTC and VITC received by the receiver 12 directly pass the receiver3 to be outputted from the LTC output terminal 18 and the VITC outputterminal 20 to outside. In that case, the LTC is supplied to the secondchecking information retrieving unit 13. The VITC is supplied to thechecking data retrieving unit 15 and the VITC error detecting unit 17.

First, a method of detecting errors in the received VITC is described.The VITC error detecting unit 17 retrieves a CRC cord from the VITCinput from the receiving unit 12, and thereby executes the cyclicredundancy check to detect the presence or absence of errors in thereceived VITC. The VITC error detecting unit 17 outputs the detectionresult from a VITC error detection result output terminal 21 to outside.

Second, a method of detecting errors in the received LTC is described.The second checking information retrieving unit 13 retrieves a collatinginformation from the LTC supplied via the receiving unit 12. Thecollating information is retrieved from the LTC at every frame therein.At the time of the retrieval, the second checking information retrievingunit 13 retrieves the collating information at the same retrievingpositions as those of the retrieval of the checking information by thefirst checking information retrieving unit 9 so that the data content ofthe collating information is substantially identical with that of thechecking information. Hereinafter, the collating information retrievedby the second checking information retrieving unit 13 is referred to asA′–D′.

The collating information, A′–D′, retrieved by the second checkinginformation retrieving unit 13 is supplied to the collating datacreating unit 14. A checking formula identical to the one stored in thechecking data creating unit 10 is precedently set and stored in thecollating data creating unit 14. The collating data creating unit 14executes a calculation processing to the supplied collating informationA′–D′ according to the stored checking formula. It is hereby, as well asin the checking data creating unit 10 described above, assumed that acalculation result (A′+B′+C′+D′) is obtained according to thecalculation processing using an addition.

The collating data creating unit 14 outputs the calculation result(A′+B′+C′+D′) to the verifying unit 16 as a collating data.

For reference, when the calculation is executed and the calculationresult produces a large quantity of data, the information of a few lowerbits in the calculation result (A′+B′+C′+D′) (eg. eight bits) may beemployed as the calculation result as in the checking data creating unit10. It is noted that a common processing should obviously be adopted inboth the checking data creating unit 10 and the collating data creatingunit 14.

Meanwhile, the checking data retrieving unit 15 retrieves the checkingdata from the VITC received by the receiving unit 12. The checking datais retrieved from the VITC at every frame therein. In the transmitter 2,the checking data is, for example, written in the user's bit in theVITC, therefore the checking data retrieving unit 15 retrieves thechecking data from the received VITC at the checking data writingposition therein (user's bit or the like). The checking data retrievingunit 15 supplies the retrieved checking data to the verifying unit 16.

The verifying unit 16 collates the checking data supplied by thechecking data retrieving unit 15 with the collating data supplied by thecollating data creating unit 14 at every frame. The verifying unit 16,when both data are identical, decides that there is no error in theframe position of the LTC. On the contrary, the verifying unit 16, whenthe data are not identical, decides that there are errors of any kind inthe frame position of the LTC. The verifying unit 16 outputs the errordetection result from the verification result output terminal 19 to theoutside of the receiver 3.

The timecode transmission apparatus according to the mode for executingthe present invention, through the error detection steps describedabove, outputs errors occurred in the VITC and LTC having beentransmitted. Of these errors detected, the errors in the VITC can bedetected with high accuracy because the CRC code is used. Thus, when itis decided there is no error present in the VITC, it can be concludedthat the checking data in the LTC, which is superimposed on the VITC andretrieved therefrom after the transmission, has no errors.

Accordingly, when it is decided by the VITC error detecting unit 17 thatthere is not error present in the VITC having been transmitted, theerror detection in the LTC can be regarded as accurate. This leads tothe decisions stated below based on the verification results by the VITCerror detecting unit 17 and verifying unit 16.

When the VITC error detecting unit 17 decides errors being present, itcan be concluded that errors are present in the VITC having beentransmitted, and the LTC error detection by the verifying unit 16 isimpossible.

When the VITC error detecting unit 17 decides no errors being present,it can be concluded that the. VITC having been transmitted does notinclude any error, and the LTC error detection by the verifying unit 16is highly accurate.

Moreover, in the timecode transmission apparatus 1 according to the modefor executing the present invention, the places of error occurrence aredetectable because of having uniformly set the retrieving positions ofthe checking and collating information, which the checking and collatingdata are respectively based on.

In this case, the checking information and the collating information areretrieved at every frame, which enables identifying errors in the LTCper frame for detection. To be able to detect errors per frame offersthe following advantage when executing a format conversion. Whenexecuting a format conversion resulting in an increased number of framesper second, effective frames are, as described earlier, scattered in aframe image data. The described condition may require, depending on thecircumstances, an anomalistic timecode capable of stepping per effectiveframe. In the case of transmitting such a timecode, the transmissionmethod (transmission apparatus) according to the present inventioncapable of detecting errors per frame is especially effective.

As described so far, the LTC error detection, which has been impossible,can be achieved by the timecode transmission apparatus according to thepresent invention. In addition to being able to detect the erroroccurrence during the timecode transmission, the following errors aredetectable.

The timecode transmission apparatus 1 is capable of detectinginconsistencies in a relationship between an image and LTC caused by anediting process implemented with respect to VITC (including image data)during the transmission or a replacement process or the like implementedwith respect to the LTC during the transmission. Such inconsistenciesinclude, not only those in a relationship between timecode components inthe LTC and the image, but also those in a relationship between an imageauxiliary information written in the user's bit of the LTC and theimage.

In addition, in the described mode for executing the invention, errorsin the LTC are detected per frame unit by creating the checking and thecollating data per frame first, to later verify them. However, errordetection intervals are, of course, not limited to frame units and canbe optionally set. In the described mode for executing the invention,again, a plurality of the checking and collating information isrespectively retrieved to create the checking and collating data,however, a single checking and collating information can be retrieved tocreate the checking and collating data. In such a case, it isunnecessary to execute the calculation processing to create the checkingand collating data. The checking and collating information can bedirectly used as the checking and collating data respectively.

POSSIBILITY OF INDUSTRIAL APPLICATION

The present invention enables error detection in LTC, which has so farbeen impossible. When one of LTC and VITC is modified in an editing ordubbing process, inconsistencies may occasionally be generated in arelationship between those timecodes. The present invention furtherenables identifying such inconsistencies.

1. A method of transmitting a timecode for simultaneously transmittingcorrelated LTC (Linear Time Code) and VITC (Vertical Interval Time Code)comprising: as a pre-processing step when transmitting a timecode, astep of retrieving a checking information from the LTC and creating achecking data using the retrieved checking information; and a step ofsuperimposing the checking data on the VITC; as a post-processing stepafter having received a timecode, a step of retrieving a collatinginformation corresponding to the checking information from the receivedLTC to create a collating data using the retrieved collatinginformation; and a step of retrieving the checking data from thereceived VITC and collating the retrieved checking data with thecollating data to verify the presence or absence of errors in thereceived LTC.
 2. The method of transmitting a timecode according toclaim 1, wherein in the pre-processing step when transmitting atimecode, the checking information is retrieved from the LTC at presetretrieving positions therein and the checking data is superimposed onthe VITC at entry positions corresponding to the retrieving positions inthe LTC, and in the post-processing step after having received a timecode, the collating information is retrieved from the received LTC atthe retrieving positions therein.
 3. The method of transmitting atimecode according to claim 2, wherein the retrieving positions are setper frame unit in an image signal.
 4. The method of transmitting atimecode according to claim 2, wherein a plurality of the checkinginformation is retrieved at each of the retrieving positions and theretrieved plural checking information are calculated based on a presetcalculation formula to create the checking data, a plurality of thecollating information is retrieved at each of the retrieving positionsand a calculation processing is executed to the retrieved pluralcollating information based on the same formula as the presetcalculation formula to create the collating data.
 5. The method oftransmitting a time code according to claim 1, wherein the checkinginformation and the collating information are retrieved from a user'sbit in the LTC.
 6. An apparatus for transmitting a timecode forsimultaneously transmitting correlated LTC (Linear Time Code) and VITC(Vertical Interval Time Code) comprising a transmitter and a receiver,the transmitter comprising: a checking data creating apparatus forretrieving a checking information from the LTC to create a checking datausing the retrieved checking information; and a superimposing apparatusfor superimposing the checking data on the VITC, the receivercomprising: a collating data creating apparatus for retrieving acollating information corresponding to the checking information from thereceived LTC to create a collating data using the retrieved collatinginformation; and a verifying apparatus for retrieving the checking datafrom the received VITC and collating the retrieved checking data withthe collating data to verify the presence or absence of errors in thereceived LTC.
 7. The apparatus for transmitting a timecode according toclaim 6, wherein the checking data creating apparatus retrieves thechecking information from the LTC at preset retrieving positionstherein; the superimposing apparatus superimposes the checking data onthe VITC at entry positions therein corresponding to the retrievingpositions in the LTC, and the collating data creating apparatusretrieves the collating information from the received LTC at theretrieving positions therein.
 8. The apparatus for transmitting atimecode according to claim 7, wherein the checking data creatingapparatus and the collating data creating apparatus set the retrievingpositions per frame unit in an image signal, and the superimposingapparatus sets the entry positions per frame unit in an image signal. 9.The apparatus for transmitting a timecode according to claim 7, whereinthe checking data creating apparatus, after having retrieved the pluralchecking information at every retrieving position, executes acalculation processing to the retrieved plural checking informationbased on a preset calculation formula to create the checking data, andthe collating data creating apparatus, after having retrieved the pluralcollating information at every retrieving position, executes acalculation processing to the retrieved plural collating informationbased on the same calculation formula as the calculation formula tocreate the collating data.
 10. The apparatus for transmitting a timecodeaccording to claim 6, wherein the checking data creating apparatusretrieves the checking information from a user's bit in the LTC, and thecollating data creating apparatus retrieves the collating informationfrom the user's bit in the LTC.